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Biomedical subjects

D P Mass

Publications and source records attributed to D P Mass.

At least 19 recordsLinked to original sources
PubMed2000

A comparison of four repair techniques for Camper's chiasma flexor digitorum superficialis lacerations: tested in an in vitro model.

The relative strengths of 4 methods for repair of the flexor digitorum superficialis tendon were examined in 14 fresh-frozen cadaver hands (40 tendons). All tendons underwent sharp zone II transection at Camper's chiasma. All transections were repaired with 4.0 Ethibond (Ethicon Inc, Sommerville, NJ) using modified Becker, modified Kessler, horizontal mattress, or simple sutures. Flexion of the repaired digit at a constant excursion rate was rendered up to tendon rupture. The modified Becker technique withstood breaking forces (57.9 N) significantly greater than the other techniques examined. Forces up to 34 N have been measured in vivo during unresisted active finger motion. Thus, the modified Becker technique appears to provide adequate strength for early active flexor digitorum superficialis motion.

Analysis of Variance↗
PubMed2000

Cyclical testing of zone II flexor tendon repairs.

Kessler, Strickland, or modified Becker repairs, all augmented with a running circumferential epitenon suture, were performed for simulated zone II flexor tendon lacerations in the index, long, and ring fingers of 12 fresh-frozen cadaveric specimens. Each hand was tested with a tensiometer built for curvilinear testing of human flexor tendons in an intact hand. Each tendon was cycled 100 times, then examined for gapping before testing to failure. Maximum load to failure, including tendon load and pinch force, was recorded for each tendon. We propose that combining the advantages of cyclical testing and a curvilinear model is the most effective way of testing flexor tendon repairs capable of undergoing an early active motion protocol. None of the repaired tendons failed during the cyclic portion of testing. The average gapping after cycling for the 3 suture techniques was 0.12 +/- 0.35 mm for the Kessler technique, 0. 00 +/- 0.00 mm for the Strickland technique, and 0.19 +/- 0.26 mm for the modified Becker technique. The maximum tendon loads to failure were 33.8 +/- 6.8 N for the Kessler technique, 30.4 +/- 5.64 N for the Strickland technique, and 76.3 +/- 9.02 N for the modified Becker technique. There was a statistically significant difference between the modified Becker repair and the other 2 repairs for maximum tendon load and pinch force to failure. The results of this study show that all 3 tendon repair techniques can withstand forces reported with passive motion, but only the modified Becker repair allows sufficient strength above those forces that are estimated for active motion during tendon healing.

Biomechanical Phenomena↗
PubMed2000

The effects of transection and reconstruction of the ulnar collateral ligament complex on the position of the proximal phalanx of the thumb during simulated tip pinch.

Injuries to the ulnar collateral ligament (UCL) of the metacarpophalangeal joint of the thumb are common and may result in functional instability of the joint. Eight cadaveric hands were studied. Physiologic levels of muscle loads were applied to the extrinsic flexor tendon of the thumb to simulate tip pinch of the thumb. We investigated the effects of transection of the UCL and accessory UCL (UCL complex) with and without transection of the dorsal capsule and volar plate and of reconstruction of the UCL, for 2 surgical techniques, on the position of the proximal phalanx with respect to the thumb metacarpal. The spatial positions of the metacarpal and proximal phalanx were measured with a 6 degrees of freedom digitizing system for flexion angles from 0 degrees to 60 degrees in 15 degrees increments. Transection of the UCL complex, dorsal capsule, and volar plate (ulnar capsuloligamentous structures) of the metacarpophalangeal joint did not affect radioulnar deviation or radioulnar shift, but did produce significant increases in supination by 8 degrees and volar translation by 2 mm at 45 degrees and 60 degrees compared with those found for the intact joint. The UCL was reconstructed with a tendon graft using the autogenous extensor digiti quinti. The first surgical technique, a traditional technique, and the second surgical technique, a technique based on anatomy, returned the position of the proximal phalanx on the metacarpal head to normal, with the exceptions of volar translation of the proximal phalanx at 60 degrees and trends toward abnormal supination of the proximal phalanx for flexion angels of 45 degrees and 60 degrees.

Adult↗
PubMed2000

Effects of reconstructed radial collateral ligament on index finger mechanics.

Twenty fresh frozen hand specimens from cadavers were studied. Physiologic levels of extrinsic muscle loads were applied to the extrinsic flexor tendons of the index finger to simulate tip pinch of the finger on a fixed plate. The acute effects of transection of the radial collateral ligament and accessory radial collateral ligament (radial collateral ligament complex) with and without transection of the dorsal capsule and volar plate on the position of the proximal phalanx with respect to the metacarpal bone of the index finger were investigated. The acute effects of reconstruction of the radial collateral ligament, for each of two different surgical techniques, on the position of the proximal phalanx also were investigated. The spatial positions of the metacarpal bone and proximal phalanx were measured with a six-degree-of-freedom digitizing system for flexion angles from 0 degrees to 90 degrees in increments of 15 degrees. Transection of the radial collateral ligament complex resulted in significant increases in ulnar deviation (adduction) of the proximal phalanx and in volar translation. Additional transection of the dorsal capsule and volar plate caused significant increases in ulnar deviation, pronation, volar translation, and ulnar shift. The first surgical technique, one traditionally used to reconstruct the metacarpophalangeal joint of the thumb, failed to return the three-dimensional position of the proximal phalanx on the metacarpal head of the index finger to normal. The second surgical technique, based on anatomy, returned the position of the proximal phalanx to levels not statistically different from normal for most flexion angles.

Adult↗
PubMed2000

A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans.

This article reports the first randomized prospective multicenter evaluation of a bioabsorbable conduit for nerve repair. The study enrolled 98 subjects with 136 nerve transections in the hand and prospectively randomized the repair to two groups: standard repair, either end-to-end or with a nerve graft, or repair using a polyglycolic acid conduit. Two-point discrimination was measured by a blinded observer at 3, 6, 9, and 12 months after repair. There were 56 nerves repaired in the control group and 46 nerves repaired with a conduit available for follow-up. Three patients had a partial conduit extrusion as a result of loss of the initially crushed skin flap. The overall results showed no significant difference between the two groups as a whole. In the control group, excellent results were obtained in 43 percent of repairs, good results in 43 percent, and poor results in 14 percent. In those nerves repaired with a conduit, excellent results were obtained in 44 percent, good results in 30 percent, and poor results in 26 percent (p = 0.46). When the sensory recovery was examined with regard to length of nerve gap, however, nerves with gaps of 4 mm or less had better sensation when repaired with a conduit; the mean moving two-point discrimination was 3.7 +/- 1.4 mm for polyglycolic acid tube repair and 6.1 +/- 3.3 mm for end-to-end repairs (p = 0.03). All injured nerves with deficits of 8 mm or greater were reconstructed with either a nerve graft or a conduit. This subgroup also demonstrated a significant difference in favor of the polyglycolic acid tube. The mean moving two-point discrimination for the conduit was 6.8 +/- 3.8 mm, with excellent results obtained in 7 of 17 nerves, whereas the mean moving two-point discrimination for the graft repair was 12.9 +/- 2.4 mm, with excellent results obtained in none of the eight nerves (p < 0.001 and p = 0.06, respectively). This investigation demonstrates improved sensation when a conduit repair is used for nerve gaps of 4 mm or less, compared with end-to-end repair of digital nerves. Polyglycolic acid conduit repair also produces results superior to those of a nerve graft for larger nerve gaps and eliminates the donor-site morbidity associated with nerve-graft harvesting.

Absorbable Implants↗
PubMed1999

The biomechanical effects of angulated boxer's fractures.

Many clinical studies have demonstrated that in the conservative care of boxer's fractures (casting, with or without reduction), between 20 degrees and 70 degrees of dorsal angulation is acceptable. This biomechanical study characterized how boxer's fracture angulation affects the ability of the intrinsic muscles to initiate grip. The flexor digiti minimi and third volar interosseous were modeled in this study. Muscular excursion of the intrinsics were modeled with a cable and sheath device. Metacarpophalangeal joint flexion per unit excursion curves were collected when the metacarpal neck was at a fracture angle of 0 degree, 15 degrees, 30 degrees, 45 degrees, 60 degrees, and 75 degrees . As fracture angles increased, the distance between the origin and insertion of the flexor digiti minimi decreased, creating shortening, or slack, of the modeled muscle. Slack was defined as excursion generating no joint flexion. Muscle shortening data were integrated with Jacobsen's muscle fiber length data and Elftmann's fiber length/tension relationship to estimate how the fracture angle affects the initiation of metacarpophalangeal joint flexion and the strength of grip. According to this model's data, fracture angles of up to 30 degrees are compatible with nearly normal mechanics. A 30 degrees angulation is associated with a flexor digiti minimi grip strength of 92% maximum and preserves 78% of the intact finger's range of motion. We therefore conclude that 30 degrees is the upper limit for acceptable final angulation.

Cadaver↗
PubMed1998

A randomized biomechanical study of zone II human flexor tendon repairs analyzed in a linear model.

Komanduri et al showed that dorsal tendon repairs using Kessler and Bunnell techniques were stronger than the standard volar repair (J Hand Surg 1996;21 A:605-611). They concluded that when testing in the anatomic curvilinear mode, the differences in strength were due to tension banding. Soejima et al challenged that concept by stating that the difference in strength was in the biomechanics of the dorsal tendon itself (J Hand Surg 1995;20A:801-807). We set out to confirm Soejima et al's theory by using more core suture techniques. We compared the tensile strength at 2-mm gap and the ultimate tensile strength of Kessler, Strickland, Robertson, and modified Becker sutures. Ten repairs of each suture type were placed either dorsally or volarly in matched human cadaver flexor tendons. There was no statistical difference between volar and dorsal placement for either maximum tensile force or force at 2-mm gap. Our study does not confirm Soejima et al's in any of the four suturing techniques.

Biomechanical Phenomena↗
PubMed1998

A randomized biomechanical study of zone II human flexor tendon repairs analyzed in an in vitro model.

To study the effect of dorsally placed flexor tendon repairs on human cadaver tendons, we used the Kessler, Strickland, Robertson, and modified Becker techniques. The strengths of the repairs were tested in a previously described human cadaveric curvilinear model. There were statistically significant increases in dorsal versus volar grasping strength with the Kessler repair (38 N vs 33 N) and the Robertson repair (51 N vs 43 N). There were no differences with the locking Strickland and modified Becker repairs. One may infer that the locking techniques are intrinsically tighter and may not be as susceptible to the different forces between the tensile and compressive surfaces of a dynamic flexor tendon.

Cadaver↗
PubMed1997

A biomechanical study of the flexor digitorum superficialis: effects of digital pulley excision and loss of the flexor digitorum profundus.

Many reports have been devoted to characterizing the significance of the pulleys for the flexor digitorum profundus (FDP). However, no comparable work has been published on the flexor digitorum superficialis (FDS). This study characterized the FDS in a human cadaver model. Eleven fresh-frozen cadaver hands were used. By using a tensiometer, data were gathered for tendon excursion, tendon load, and work of flexion. Changes in efficiency were caused by excision of annular pulleys A1, A2, A3, and the palmar aponeurotic pulley. We also measured the effect of FDP excision on FDS efficiency. Sectioning of the A2 and A3 pulleys together caused statistically significant losses of efficiency in all three parameters (work, load, and excursion). When the FDP was removed from a finger with an intact pulley system, losses in both work and excursion efficiencies were significant. Removing the FDP while cutting different pulleys caused significant decrease in FDS excursion efficiency. We conclude that A2 and A3 are the most important pulleys for maintaining normal FDS function, and that the presence of the FDP in the digital sheath is essential for optimal FDS excursion efficiency.

Biomechanical Phenomena↗
PubMed1996

Tensile strength of flexor tendon repairs in a dynamic cadaver model.

Twenty-six fresh-frozen cadaver hands (78 tendons) underwent sharp zone II profundus tendon transection and repair with Bunnell, Kessler, Kessler with circumferential epitenon, or epitenon-alone sutures. Suture assignment was randomized, and core sutures were placed either palmarly or dorsally (also randomized) within the flexor tendon. Ten trials of each suture type and placement were performed. Flexion of the repaired digit at a constant excursion rate was performed up to tendon rupture. In all cases, dorsally placed sutures provided significantly more tensile strength than palmarly placed sutures. In light of the previous evidence that tendon viability is dependent on diffusion and not dependent on the vascular supply, we believe that a dorsally placed core suture and circumferential epitenon repair for zone II profundus repairs should be considered because of their increased strength. All future testing of tendon repairs should be performed in an anatomic "curvilinear" model because it simulates the specific biomechanical conditions that are unique to the flexing digit.

Cadaver↗
PubMed1996

Biomechanical changes of cadaveric finger flexion: the effect of wrist position and of the transverse carpal ligament and palmar and forearm fasciae.

This study was designed to investigate whether the position of the wrist or sectioning of the transverse carpal ligament (TCL), as well as the palmar fascia and forearm fascia, modifies the biomechanical behavior of the finger flexion, as defined by changes of excursion, load (force), and work of the flexor tendons. The parameters were measured in fresh-frozen cadaver hands with the wrist in 30 degree extension, neutral, and 30 degree flexion, before and after division of the TCL. Having the wrist in extension improved excursion efficiency, whereas flexing the wrist produced the opposite effect, with a 16% decrease in excursion efficiency after division of the TCL. Change in excursion efficiency between the intact and cut TCL was 8% in the flexed position, 5% in the neutral position, and 0.3% in the extended position. Change in load efficiency between intact and cut TCL was 11% in the flexed position, 6% in the neutral position, and 0% in the extended position. Change in the work efficiency between intact and cut TCL groups was noted most with the wrist in the flexed position (13%), compared to a small change (3%) in neutral wrist position and no change in wrist extension. A significant decrease in the excursion efficiency of the flexor tendons was demonstrated when the wrist was in the flexed position. Any increase in the excursion of the flexor tendons could clinically result in decreased grip strength when the wrist is flexed. Furthermore, the effects of TCL division were not significant when wrist position was in extension.

Biomechanical Phenomena↗
PubMed1995

The flexor synovial sheath anatomy of the little finger: a macroscopic study.

Anatomy texts describe the flexor synovial sheath of the little finger as extending proximally into the palm to join with the ulnar bursa in 80% of cases. Based on this, one would expect frequent extension of little finger flexor synovial sheath infections into the forearm. Methylene blue injection followed by open tenogram was used to define the anatomy of the flexor synovial sheath of the little finger in 60 cadaver hands. In 27 hands, the flexor synovial sheath extended proximally from the bony profundus tendon insertion to terminate at the palmar aponeurosis pulley. A stricture of varying length separated the flexor synovial sheath from the more proximal ulnar bursa. In 19 hands, the flexor synovial sheath was continuous with the ulnar bursa, conforming to the conventional textbook description. In 14 hands, the flexor synovial sheath stopped at the proximal border of the A1 pulley. An inconsistent defect from 1 to 10 mm was noted. The clinical implications of these findings suggest that many little finger flexor synovial sheath infections, when caught early and after careful physical examination, need only be managed by drainage at the distal palmar level.

Cadaver↗
PubMed1994

Rescue of reapproximated flexor profundus tendons in vitro following segmental irradiation.

Segments of rabbit flexor profundus tendon were transected at their zone II midpoints. Before reapproximation, proximal and/or distal segment halves received 10,000 rads of x-radiation. Four treatment groups were examined with light and electron microscopy after 2, 4, and 8 weeks in culture: group XX had proximal and distal tendon halves irradiated, group PX had only distal tendon halves irradiated, group XD had only proximal tendon halves irradiated, and group PD served as nonirradiated control tendons. After 2 weeks, the epitenons of all nonirradiated segments had proliferated to become several cell layers thick with migratory-type cells. By 4 weeks these cells in groups PX and XD crossed the repair site and invaded the opposing irradiated segments in a previously undescribed pattern. By 8 weeks, bridging and remodeling of the repair site were evident in groups PX and XD, yet not to the extent noted in the nonirradiated control group PD. No histologically evident difference in mechanism or completeness of healing was observed between groups PX and XD, and no comparable proliferation, bridging, or remodeling was observed in the completely irradiated group XX. These observations allowed for conclusions to be drawn regarding regional involvement during intrinsic tendon healing and confirmed the pluripotency of poorly differentiated epitenocytes.

Animals↗
PubMed1993

Effect of hyaluronic acid on rabbit profundus flexor tendon healing in vitro.

We performed an in-depth biomechanical evaluation of the effect of hyaluronic acid (HA) on the healing of rabbit profundus tendons cultured in vitro. Seventy-eight flexor tendons from 13 rabbits were transected and reapproximated at their Zone II midpoints. Tendons were divided into left and right forepaw groups. Each tendon from the left forepaw group was incubated in one of four possible culture media: control (no HA), low (0.1 mg/ml), medium (0.5 mg/ml), or high (1.0 mg/ml) HA media. HA was added on the first day of incubation. Each tendon from the right forepaw group was cultured in low, medium, or high concentrations of HA, but HA was added after 1 week of incubation in control media. All tendons were cultured for 8 weeks, after which time tenorrhaphies were disrupted and the following biomechanical parameters were determined: apparent maximum stress, apparent strain at apparent maximum stress, normalized energy absorption, and tangent modulus before failure. Comparisons using these parameters showed no statistically significant differences among the various tendon groups. We believe this is the first study of its kind to show no effect of hyaluronic acid on the functional strength of tendon after healing in vitro.

Animals↗
PubMed1993

Effects of constant mechanical tension on the healing of rabbit flexor tendons.

The biomechanical effects of constant mechanical load on tendon repair in vitro were determined for rabbit flexor tendons. Tendons were removed from Zone II, transected, reapproximated with four simple sutures, and cultured in standard medium. Tendons from the right forelimbs were loaded with 3.1-g weights; tendons from the contralateral forelimbs served as unloaded tendons. Tenorrhaphies were disrupted at zero, one, three, and six weeks postsuturing by fixed-speed tensiometry. True maximum stress (strength), normalized energy absorbed, and tangent modulus steadily increased over time, becoming significantly greater than unincubated controls in the loaded and unloaded groups at six weeks. True strain at maximum stress increased with duration for unloaded tendons; after six weeks it was significantly greater than unincubated control tendons. This study demonstrates a method for quantifying the biomechanics of tendon after intrinsic tendon segment healing and presents the first biomechanical evaluation of constant tension applied across the laceration site during an in vitro healing phase.

Animals↗
PubMed1992

Full-thickness skin wound explants in tissue culture: a mechanical evaluation of healing.

This study was designed to evaluate biomechanically defined wound healing in full-thickness skin explants in tissue culture. The requirement for preculture incubation of wounds in situ was characterized. Full-thickness skin incisions were made in 44 rats and closed immediately. Wounds were incubated in situ for 0, 12, 24, 36, 48, 72, or 96 hours before harvesting and placement into tissue culture media for 6 weeks. Healing was evaluated by biomechanical criteria: tensiometric distraction to wound rupture generated true stress and energy absorption data. Burst-strength (maximum true stress) and toughness (energy absorption) were five times higher in the 48-hour group than in any other group; other groups were not different from each other. This study demonstrates long-term survival of full-thickness skin in culture and shows that full-thickness skin explants heal in tissue culture. Possible explanations for the narrow window of opportunity for harvest (48 hours, no more and no less) are discussed.

Animals↗