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PubMed2002

Unilateral cervical facet dislocation: injury mechanism and biomechanical consequences.

STUDY DESIGN: Human cadaveric cervical spines were subjected to nondestructive repeated-measures flexibility tests before, during, and after unilateral facet dislocation. OBJECTIVES: To assess the relative stability and kinematics of the spine in the normal condition, after unilateral facet lock without bony injury and after reducing (unlocking) the facet dislocation. SUMMARY OF BACKGROUND DATA: Experimental unilateral facet dislocation has been studied only when associated with extensive damage to disc, bone, or both. The relative stability of the normal, locked, and unlocked cervical spine has not been studied. METHODS: Unilateral facet dislocation with minimal associated injury was created by slowly applying axial torque while specimens were bent laterally and flexed. Before and after injury, nondestructive torques were applied about each anatomic axis, while three-dimensional specimen motion was recorded stereophotogrammetrically. RESULTS: Unilateral facet dislocation was created with a mean axial torque of 10.2 +/- 2.7 Nm. After locking, range of motion, lax zone, and stiff zone were significantly reduced relative to normal (P < 0.05). After unlocking, the same parameters were significantly increased relative to normal. The position of the axis of rotation shifted when the facet was locked and the centrode elongated after the facet was unlocked. CONCLUSIONS: Unilateral facet dislocation without fracture can be created with moderate loads when axial torque is applied while the facet is distracted. The spine is stable while the articular masses are locked unilaterally; however, the motion segment becomes overtly unstable after the facet dislocation is reduced.

Adult↗
PubMed2004

Dislocation after long-necked total hip arthroplasty.

Dislocation after total hip arthroplasty is problematic and not completely understood. Skirted long-necked implants have been used to reestablish soft tissue tension with the assumption that their use will reduce dislocation. It is unknown whether the dislocation rates with long-necked implants are different than those with standard neck length devices. The records of 250 consecutive total hip arthroplasties were reviewed, 125 primary and 125 revision, in which long-necked femoral prostheses were used. A matched control sample with standard neck length prostheses was defined. Dislocation rates and radiographic indices of leg length were calculated and compared with the control group. Dislocation rates in the long-necked groups were 10.6% and 18% for primary and revision surgeries, respectively. These rates were significantly higher than the rates seen in standard neck length controls (1.6% and 10%, respectively). There was no difference in leg-length discrepancy between long-necked prostheses and standard neck length matched controls. Long-necked prostheses are associated with higher rates of dislocation after total hip arthroplasty. The higher rates may be attributable to impingement of the neck, inadequate restoration of soft tissue tension, and/or other factors. Although this study cannot claim to have shown a cause and effect relationship between the skirted neck and dislocation, the association between the two variables is clearly shown.

Arthroplasty, Replacement, Hip↗
PubMed2006

Dislocation of bipolar hemiarthroplasty: rate, contributing factors, and outcome.

UNLABELLED: Dislocation of bipolar hemiarthroplasty of the hip is a rare complication. The objectives of our study were to assess the incidence, contributing factors, and outcomes of bipolar prosthesis dislocation. From 1974 to 2001, 1812 primary bipolar hemiarthroplasties were done at our institution. Seventy-four percent were done in patients with fractures of the femoral neck. An anterolateral surgical approach was used in 79% of hips, a posterolateral approach was used in 14% of hips, and a transtrochanteric approach was used in 7% of hips. Thirty-two hips dislocated. The cumulative probabilities of dislocation at 1 year, 5 years, 10 years, and 20 years were 1.1% (95% CI range, 0.6%-1.6%), 1.5% (95% CI range, 0.9%-2.1%), 2.1% (95% CI range, 1.2%-3.1%), and 5% (95% CI range, 1.9%-9.6%), respectively. There was no significant association of dislocation with the surgical approach or with the primary operative diagnosis. More than (1/2) of the dislocations occurred within 6 months postoperative. Late dislocations occurred most commonly in patients with Bateman prostheses and osteonecrosis and were associated with inner bearing dissociation. Closed reduction was successful in preventing additional surgery in only 30% of patients. The surgeon must be aware that closed reduction may be unsuccessful, and open reduction with replacement of components may be necessary. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Adolescent↗
PubMed2006

The effect of EPSTR and minimal incision surgery on dislocation after THA.

Dislocation rates after posterior approach THA have decreased with the advent of enhanced posterior soft tissue (EPSTR) repairs that incorporate the external rotators. We examined three posterior approaches (simple posterior repair, EPSTR, and posterior minimal incision surgery using enhanced posterior soft tissue repair) performed by one surgeon in 390 consecutive primary THA operations (390 patients) from 1992-2003. A simple posterior repair of the external rotators done through three drill holes was performed in the first 90 patients. EPSTR incorporating the external rotators and posterior capsule in one continuous sleeve was performed in 180 patients. A 10 cm mini incision with EPSTR was performed in 120 patients. The overall dislocation rate for the series was 2.3% (9 of 390 procedures) with a 1% (4 of 390 procedures) revision rate for dislocation. The simple repair group had a greater dislocation rate (5.5%) compared to the group with EPSTR (1.3%) and the minimal incision with EPSTR group (1.7%). EPSTR decreased dislocation after total hip arthroplasty performed with a posterior approach. A 10 cm mini incision posterior approach with EPSTR maintained the low dislocation rate. Revision rate for dislocation was equivalent between the 3 groups.

Adult↗
PubMedDate not supplied

Natural history of glenohumeral dislocation--revisited.

The purpose of this study was to evaluate the natural history of glenohumeral dislocation in young athletes. A review of the literature revealed a consensus of opinion that the dislocated shoulder should be immobilized from 3-6 weeks. However, a high recurrence rate could be expected. One hundred twenty-one patients with acute traumatic anterior dislocations were evaluated (average age-19 years). Methods of immobilization were shoulder immobilizers and slings and swaths. Sixty-two patients were immobilized and 56 (90%) of these suffered recurrent dislocation. Fifty-nine patients were not immobilized and 50 (85%) re-dislocated their shoulders. The length of immobilization had no effect on the recurrence rate. All re-dislocations occurred within 18 months of the initial injury. Seventy-nine patients were operated on for recurrent dislocation. With such a high recurrence rate in the athletic age group, the authors question if immobilization affects the prognosis.

Adolescent↗
PubMedDate not supplied

Anterior dislocation of the shoulder joint sustained through skiing. Arthrographic findings and prognosis.

Over a period of 10 years we have studied 14,952 cases of skiing injuries. Of these, 660 cases (4.5%) were injuries to the shoulder with 291 cases (44.1%) being anterior dislocations of the shoulder. One hundred forty-three cases revealed an initial dislocation (49.1%), and 148 cases were recurrent dislocations (50.9%). We examined the arthrography of the dislocated shoulder in 89 cases. Of these initial dislocations, one-half of the capsular detachment type were redislocated, but no redislocation had occurred in the capsular tear type. In addition, almost all of the recurrent cases were of the capsular detachment type. Thus, through arthrography of the anterior dislocated shoulder, we have been able to discover the mechanism of the dislocation and decide upon the necessary duration and method of fixation of the shoulder after reduction.

Adolescent↗
PubMedDate not supplied

Operative treatment of posterior shoulder dislocations by posterior glenoidplasty, capsulorrhaphy, and infraspinatus advancement.

Posterior dislocations of the shoulder are rare, comprising only 4% of shoulder dislocations. Several operative procedures have been described in treating recurrent dislocations, and results have been varied. A retrospective review of eight shoulders in eight patients treated by posterior glenoidplasty with capsulorrhaphy and infraspinatus advancement revealed generally good results. Followup ranged from 10 to 114 months, with an average of 36 months. Seven patients were classified as recurrent traumatic dislocators and one as a recurrent atraumatic voluntary dislocator. Results graded as good, fair, and failure were based on pain, range of motion, return to activities, recurrence, and roentgenograms. Six patients had good results with return to full activity, full range of motion, no pain, no recurrence, and no degenerative changes of roentgenograms. One patient, who has not returned to athletic activities and has occasional pain and limited range of motion, was graded as a fair result. The patient classified as an atraumatic voluntary dislocator has occasional feelings of instability and slight pain with strenuous activity, but has not had a recurrence and has no difficulty with activities of daily living. She was also classified as a fair result. There have been no recurrences or degenerative changes on followup radiographs. Computerized tomography performed on two patients documented a definite change in orientation of the glenoid. We feel that glenoidplasty with capsular reefing and infraspinatus advancement, if performed carefully, provides an excellent operative treatment for recurrent posterior dislocations of the shoulder.

Adolescent↗
PubMedDate not supplied

Treatment of acute patellar dislocation.

To determine the effectiveness of nonoperative and operative treatment of initial acute patellar dislocation, we reviewed the charts of 399 patients with the diagnosis of an acute dislocation, seen during a 30 year period. One hundred patients (103 knees) met the criteria for inclusion in the study. The average age of the patient at injury was 21.7 years (range, 9 to 72 years). Length of followup averaged 8 years (range, 2 to 26 years). Retrospectively, we divided the patients into two groups, according to the examination of their unaffected knee. Group I (69 knees) showed evidence on examination of congenital abnormality of the extensor mechanism in the unaffected knee, indicating a predisposition to dislocate with less significant trauma. Group II (34 knees) showed no clinically perceptible congenital predisposition to dislocate based on examination of the unaffected knee. In the nonoperatively treated knees in Group I, there was a 52% (28/54) incidence of good or excellent results. The nonoperatively treated knees in Group II had a 75% (15/20) incidence of good or excellent results. Acute dislocation occurred more frequently in males than in females. Recurrence was rarer in patients whose initial dislocation had occurred when they were over 15 years old. Contrary to recently published reports, primary acute traumatic patellar dislocations can be treated with nonoperative therapy with good or excellent results. Initial evaluation should include examination of the uninvolved knee which, if found to have signs of congenital abnormality, would indicate a worse prognosis.

Adolescent↗
PubMed1982

Dislocation of the hip in trisomy 21.

Almost one child in twenty with trisomy 21 will develop spontaneous dislocation of the hip between learning to walk and the age of 10 years. After the age of two years spontaneous habitual dislocation may occur. If left untreated, acute dislocation, subluxation and fixed dislocation follow in sequence. The natural history of the condition is described and the clinical and radiological features of 45 dislocations in 28 patients are presented. Nineteen had received no treatment. The most effective treatment was found to be pelvic or femoral osteotomy, combined with capsular plication, carried out in the phase of habitual dislocation. Once subluxation or fixed dislocation was present, the results of operation were poor and it is not recommended. All patients, even if left untreated, remain mobile. Pain is not a prominent feature.

Adolescent↗
PubMed1998

Fracture-dislocation of the fifth lumbar vertebra. A new classification.

We have studied fracture-dislocation of the fifth lumbar vertebra in seven patients and reviewed 50 previously reported cases. Based on this information, we have classified the injury into five types: type 1, unilateral lumbosacral facet-dislocation with or without facet fracture; type 2, bilateral lumbosacral facet-dislocation with or without facet fracture; type 3, unilateral lumbosacral facet-dislocation and contralateral lumbosacral facet fracture; type 4, dislocation of the body of L5 with bilateral fracture of the pars interarticularis; and type 5, dislocation of the body of L5 with fracture of the body and/or pedicle, with or without injury of the lamina and/or facet. Conservative treatment of fracture-dislocation of L5 is generally not effective because the lesion is fundamentally unstable. Planning of the operation should be made on the basis of the various types of injury.

Adolescent↗
PubMed1999

Total dislocations of the navicular: are they ever isolated injuries?

Isolated dislocations of the navicular are rare injuries; we present our experience of six cases in which the navicular was dislocated without fracture. All patients had complex injuries, with considerable disruption of the midfoot. Five patients had open reduction and stabilisation with Kirschner wires. One developed subluxation and deformity of the midfoot because of inadequate stabilisation of the lateral column, and there was one patient with ischaemic necrosis. We believe that the navicular cannot dislocate in isolation because of the rigid bony supports around it; there has to be significant disruption of both longitudinal columns of the foot. Most commonly, an abduction/pronation injury causes a midtarsal dislocation, and on spontaneous reduction the navicular may dislocate medially. This mechanism is similar to a perilunate dislocation. Stabilisation of both medial and lateral columns of the foot may sometimes be essential for isolated dislocations. In spite of our low incidence of ischaemic necrosis, there is always a likelihood of this complication.

Adult↗
PubMed1998

Snapping of the medial head of the triceps and recurrent dislocation of the ulnar nerve. Anatomical and dynamic factors.

We describe seventeen patients (twenty-two limbs) who had snapping (dislocation) of both the ulnar nerve and the medial head of the triceps over the medial epicondyle. Two patients (two limbs) were seen because of painless snapping, four patients (five limbs) had snapping and pain in the medial aspect of the elbow, three patients (three limbs) had symptoms related to the ulnar nerve only, and six patients (seven limbs) had snapping and symptoms related to the ulnar nerve. In addition, snapping was identified incidentally on routine screening in five asymptomatic limbs in four patients, one of whom was seen because of snapping and symptoms related to the ulnar nerve on the contralateral side. The diagnosis was confirmed with magnetic resonance imaging or computerized tomography, or both, in all but the first three patients, in whom the operative findings were confirmatory. Only six patients (seven limbs) were sufficiently symptomatic to be managed operatively. Of these six patients, five (six limbs) who had symptoms related to the ulnar nerve had lateral transposition or excision of the dislocating medial head of the triceps in addition to decompression and transposition of the ulnar nerve. Two of these patients had had persistent symptoms immediately after a previous transfer of the ulnar nerve performed at another institution for symptoms related to, and well documented dislocation of, the ulnar nerve; we performed the index procedure to correct the postoperative snapping, which was the result of an unrecognized dislocation of the medial head of the triceps in one patient and the result of an accessory triceps tendon in the other. One patient who had pain in the medial part of the elbow, snapping (without symptoms related to the ulnar nerve), and cubitus varus had a valgus osteotomy of the distal aspect of the humerus that corrected the line of pull of the triceps and relieved the snapping. All of the patients who were managed operatively had an excellent result (no snapping, no symptoms related to the ulnar nerve, and a full range of motion), at an average of 4.5 years postoperatively. Non-operative treatment provided control of symptoms related to the ulnar nerve in four limbs and control of pain from the snapping in four limbs. Snapping on the medial side of the elbow, even if it is associated with symptoms related to the ulnar nerve, is not necessarily caused by dislocation of the ulnar nerve alone. Patients who have a transposition of the ulnar nerve, especially those who have dislocation of the ulnar nerve, should be examined intraoperatively with the elbow in flexion and extension so that the surgeon can be certain that the medial head of the triceps does not snap over the medial epicondyle. Failure to recognize concurrent dislocation of the ulnar nerve and the medial head of the triceps can result in persistent, symptomatic snapping after an otherwise successful transposition of the ulnar nerve.

Adolescent↗
PubMed2000

The effect of femoral component head size on posterior dislocation of the artificial hip joint.

BACKGROUND: Posterior dislocation continues to be a relatively common complication following total hip arthroplasty. In addition to technical and patient-associated factors, prosthetic features have also been shown to influence stability of the artificial hip joint. In this study, a dynamic model of the artificial hip joint was used to examine the influence of the size of the head of the femoral component on the range of motion prior to impingement and posterior dislocation following total hip replacement. METHODS: Six fresh cadaveric specimens were dissected, and an uncemented total hip prosthesis was implanted in each. Each specimen was mounted in a mechanical testing machine and loaded with use of a system of seven cables attached to the femur and pelvis that simulated the action of the major muscle groups crossing the hip joint. The hip was taken through a range of motion similar to that experienced when rising from a seated position. The three-dimensional position of the femur at the points of impingement and dislocation was recorded electronically. The range of joint motion was tested with prosthetic femoral heads of four different diameters (twenty-two, twenty-six, twenty-eight, and thirty-two millimeters). RESULTS: Significant associations were noted between the femoral head size and the degree of flexion at dislocation in ten (p = 0.001), twenty (p < 0.001), and thirty (p = 0.003) degrees of adduction. Increasing the femoral head size from twenty-two to twenty-eight millimeters increased the range of flexion by an average of 5.6 degrees prior to impingement and by an average of 7.6 degrees prior to posterior dislocation; however, increasing the head size from twenty-eight to thirty-two millimeters did not lead to more significant improvement in the range of joint motion. The site of impingement prior to dislocation varied with the size of the femoral head. With a twenty-two-millimeter head, impingement occurred between the neck of the femoral prosthesis and the acetabular liner, whereas with a thirty-two-millimeter head, impingement most frequently occurred between the osseous femur and the pelvis. CONCLUSIONS: With the particular prosthesis that was tested, increasing the diameter of the femoral head component increased the range of motion prior to impingement and dislocation, decreased the prevalence of prosthetic impingement, and increased the prevalence of osseous impingement. CLINICAL RELEVANCE: These results suggest that femoral heads with a twenty-eight-millimeter diameter increase the range of motion after total hip replacement. This may be beneficial when additional factors compromising joint stability are encountered.

Biomechanical Phenomena↗
PubMed2001

Modular component exchange for treatment of recurrent dislocation of a total hip replacement in selected patients.

BACKGROUND: Exchange of modular components is a treatment option for the correction of recurrent dislocation of a total hip replacement. In this study, we reviewed our experience with this technique in order to define patient selection criteria and to report the outcome of treatment. METHODS: Of 2935 hips treated with primary porous-coated total hip arthroplasty, fourteen (in fourteen patients) that met certain preoperative and intraoperative criteria were treated with modular component exchange because of recurrent hip instability. The primary arthroplasties in these fourteen patients had been performed through a posterior approach. At the revisions, we removed any sources of osseous or soft-tissue impingement that contributed to dislocation. Acceptable stability at the completion of component exchange was defined as stability in maximum flexion, in full extension with external rotation, and in at least 45 degrees of internal rotation with the hip in 90 degrees of flexion and maximum adduction. RESULTS: One patient was lost to follow-up. At a mean of 5.8 years (range, 2.8 to 11.8 years) after the revision, ten of the remaining thirteen patients had not had a dislocation. Of the three patients in whom the hip dislocated after the modular component exchange, only one had recurrent dislocation; thus, recurrent dislocation was eliminated in twelve of thirteen patients. CONCLUSIONS: In selected cases, modular component exchange for the treatment of recurrent hip dislocation has a success rate comparable with that of more extensive operations. This method should be considered because it avoids the morbidity associated with revision of well-fixed components. However, to ensure the appropriateness of this surgical option, each patient must be thoroughly evaluated to identify all factors that contribute to instability and adequate intraoperative stability must be achieved.

Adult↗
PubMed2004

Posterior shoulder dislocation in infants with neonatal brachial plexus palsy.

BACKGROUND: Glenoid dysplasia and posterior shoulder subluxation with resultant shoulder stiffness is a well-recognized complication in infants with neonatal brachial plexus palsy. It is generally considered to be the result of a slowly progressive glenohumeral deformation secondary to muscle imbalance, physeal trauma, or both. Recent publications about infantile posterior shoulder dislocation have suggested that the onset of dysplasia occurs at an earlier age than has been previously recognized. The prevalence of early dislocation in infants with this disorder has not been previously reported, to our knowledge. METHODS: We studied 134 consecutive infants with neonatal brachial plexus palsy who were seen at our institution over a period of two years. All infants were examined at monthly intervals to assess neurological recovery and the status of the upper extremity until recovery occurred or a treatment plan was established. The type of brachial plexus involvement was classified. Specific clinical signs associated with subluxation and dislocation were recorded. These included asymmetry of skin folds of the axilla or the proximal aspect of the arm, apparent shortening of the humeral segment, a palpable asymmetric fullness in the posterior region of the shoulder, or a palpable click during shoulder manipulation. The infants who were identified as having these clinical signs were evaluated with ultrasonographic imaging studies. RESULTS: Eleven (8%) of the 134 infants had a posterior shoulder dislocation. The mean age at the time of diagnosis was six months (range, three to ten months). There was no correlation between the occurrence of dislocation and the type of initial neurological deficit. A rapid loss of passive external rotation between monthly examinations indicated a posterior shoulder dislocation. CONCLUSIONS: Posterior shoulder dislocation can occur earlier (before the age of one year) and more rapidly in infants with neonatal brachial plexus palsy than has been appreciated previously. As with developmental dysplasia of the hip, a high index of suspicion, recognition of clinical signs, and the use of ultrasonography will allow the diagnosis to be established. Following early diagnosis, attention should be focused on improving the stability and congruency of the shoulder joint.

Brachial Plexus Neuropathies↗
PubMed2004

Salvage of a recurrently dislocating total hip prosthesis with use of a constrained acetabular component. A concise follow-up of a previous report.

We previously reported the results at a mean of five years following the use of a tripolar constrained acetabular component to treat recurrently dislocating total hip prostheses. In this study, we report the results after longer follow-up, with emphasis on the prevalence of implant loosening, osteolysis, and later recurrent instability. Fifty-five patients treated with a total of fifty-six constrained acetabular components because of recurrent dislocations of a total hip prosthesis (average, six dislocations; range, two to twenty dislocations) were followed for an average of 10.2 years (range, 7.0 to 13.2 years) or until death. Four (7%) of the fifty-six hips had a subsequent dislocation or failure of the device. Three femoral components (5%) and two acetabular components (4%) were revised because of aseptic loosening. One hip was revised because of osteolysis. We concluded that this constrained acetabular component provides durable protection against additional dislocations without substantial deleterious effects on component fixation. We use this device to treat recurrent dislocation when other modalities are unlikely to be effective.

Acetabulum↗
PubMed2005

The role of patient restrictions in reducing the prevalence of early dislocation following total hip arthroplasty. A randomized, prospective study.

BACKGROUND: It is currently unknown whether functional restrictions following total hip arthroplasty can reduce the prevalence of early postoperative dislocation. Our hypothesis was that dislocation was more likely to occur in patients who were not placed on these restrictions. METHODS: We performed a prospective, randomized study to evaluate the role of postoperative functional restrictions on the prevalence of dislocation following uncemented total hip arthroplasty through an anterolateral approach. Of the 630 eligible consecutive patients, 265 patients (303 hips) consented to be randomized into one of two groups (the "restricted" group or the "unrestricted" group). The patients in both groups were asked to limit the range of motion of the hip to <90 degrees of flexion and 45 degrees of external and internal rotation and to avoid adduction for the first six weeks after the procedure. The patients in the restricted group were instructed to comply with additional hip precautions during the first six weeks postoperatively. Specifically, these patients were managed with the placement of an abduction pillow in the operating room before bed transfer and used pillows to maintain abduction while in bed; used elevated toilet seats and elevated chairs in the hospital, in the rehabilitation facility, and at home; and were prevented from sleeping on the side, from driving, and from being a passenger in an automobile. All patients were followed for a minimum of six months postoperatively. RESULTS: There was one dislocation in the entire cohort (prevalence, 0.33%). This dislocation occurred in a patient in the restricted group during transfer from the operating table to a bed with an abduction pillow in place. Patients in the unrestricted group were found to return to side-sleeping sooner (p < 0.001), to ride in automobiles more often (p < 0.026), to drive automobiles more often (p < 0.001), to return to work sooner (p < 0.001), and to have a higher level of satisfaction with the pace of their recovery (p < 0.001) than those in the restricted group. There was an additional expenditure of approximately $655 per patient in the restricted group. CONCLUSIONS: Total hip arthroplasty through an anterolateral approach is likely to be associated with a low dislocation rate. Removal of several restrictions did not increase the prevalence of dislocation following primary hip arthroplasty at our institution. However, it did promote substantially lower costs and was associated with a higher level of patient satisfaction as patients achieved a faster return to daily functions in the early postoperative period.

Adolescent↗
PubMed1995

Complete dislocation of the knee: spectrum of associated soft-tissue injuries depicted by MR imaging.

OBJECTIVE: Complete knee dislocation is a rare injury. The purpose of this study was to evaluate the spectrum of injuries that are depicted by MR imaging in patients with a dislocation of the knee and to determine if there is any predictive factor that might indicate those patients who may be at risk for popliteal nerve injury. MATERIALS AND METHODS: A retrospective search for patients sustaining traumatic knee dislocations who had radiographs and an MR imaging examination of the knee as part of their initial evaluation was done at three level I trauma centers for the period between 1989 and 1993. Each MR examination was independently reviewed by three osteoradiologists for ligamentous, tendinous, meniscal, and osseous injuries. Equivocal diagnoses were decided by consensus. Only patients who underwent surgery were selected. MR imaging findings were confirmed at the time of surgery. Seventeen patients (15 men, two women; age range, 14-62 years; mean age, 29 years) were studied. Motor vehicle accident, fall from a height, a vehicle striking a pedestrian, and football injury were common mechanisms of injury. Posterior dislocation (seven patients) and anterior dislocation (five patients) were the most common injuries. RESULTS: At the time of surgery, all patients had complete tears of the anterior cruciate ligament, 15 had complete tears of the posterior cruciate ligament, nine had complete tears of the medial collateral ligament, and 12 had tears of the fibular collateral ligament (nine tore both the fibular collateral ligament and the biceps femoris tendon). Popliteal tendon tears occurred in eight patients (six complete, two partial). Of the six patients with complete tears of the popliteal tendon, five occurred at the musculotendinous junction; all were the result of either posterior or posterolateral dislocations. Four patients had injuries to the peroneal nerve; three of the four also had tears of the popliteal tendon. On MR imaging, the integrity of the anterior cruciate and lateral collateral ligaments was correctly depicted in all 17 patients; evaluation of the posterior cruciate ligament resulted in one false-positive and one false-negative diagnosis of a tear; evaluation of the medial collateral ligament resulted in one false-positive diagnosis of a tear; and one false-positive diagnosis of a tear occurred with evaluation of the popliteal tendon. CONCLUSION: Knee dislocations cause extensive disruption of the ligaments that stabilize the knee and the surrounding soft-tissue structures, including the popliteal artery. Nearly all will result in disruption of the cruciate ligments and, often, injury of the collateral ligaments. An injury to the popliteal tendon denotes a more severe injury. The mechanism of injury that results in a popliteal tendon tear may also increase the possibility of a peroneal nerve injury. Recognition of this pattern of injuries on MR imaging enables precautionary observation for ischemic changes of the foot to be instituted in patients that otherwise may not be considered at risk for acute vascular compromise.

Adolescent↗