Passive and active rehabilitation for partial lacerations of the canine flexor digitorum profundus tendon in zone II

Is conservative management of partial zone II flexor tendon laceration possible? A systematic literature review and meta-analysis

Background: There is still no consensus on managing zone II level partial flexor tendon lacerations, and the management of zone II partial flexor tendon injuries is controversial. No reliable large cohort studies or metaanalysis papers on partial flexor tendon laceration management are available in PubMed or Embase.Methods: We searched PubMed, Embase, Cochrane Library, Insight, Scopus, and Web of Science databases for primary research articles investigating outcomes of patients with partial flexor tendon injuries. The initial search was limited to human studies that were published from 1970-2021 and indexed as randomized controlled or clinical trials or observational, cross-sectional, or cohort studies. We used statistical package R version 4.1.2 for this meta-analysis.Results: The Standardised mean difference (SMD) of the common effects model was 2.020 (95% CI; 1.583-2.457; P < 0.0001), indicating that the results of conservative treatment without surgical intervention are similar to surgical intervention or better in some articles. The SMD of the random effect model was 7.093 (95% CI; 1.090-13.096; P < 0.0206), indicating the same result. Higgins' I2 value was 97.6%, indicating serious heterogeneity.Conclusions: In this first meta-analysis on flexor zone II conservative treatment, five papers with publication bias were analyzed. It is meaningful to verify the result of conservative treatment statistically. Even though this is a heterogeneous paper, conservative treatment seems to have a lot of benefits for the patient, including offering a fairly solid longterm prognosis with very few complications.

The Management of Partial Zone II Intrasynovial Flexor Tendon Lacerations: A Literature Review of Biomechanics, Clinical Outcomes, and Complications

BACKGROUND

Penetrating trauma or lacerations within zone II of the flexor sheath may result in partial tendon injury. The proper management of this injury is controversial; the literature contains differing indications for surgical treatment and postoperative rehabilitation.

METHODS

A literature review of the Cochrane, MEDLINE, and PubMed databases was performed using the following search criteria: partial, flexor, tendon, and laceration. All English language studies that evaluated biomechanical strength, complications, and outcomes after partial tendon injury in human and animal studies were included and reviewed by two of the authors.

RESULTS

Animal and cadaveric biomechanical studies have demonstrated that partial lacerations involving up to 95 percent of the tendon cross-sectional area can safely tolerate loads generated through unresisted, active finger flexion. Suture tenorrhaphy of partial tendon injury is associated with decreased tendon tensile strength, increased resistance, and decreased tendon gliding. Complications of nonsurgical management include triggering and entrapment, which can be managed by tendon beveling or pulley release. Late rupture is extremely uncommon (one report).

CONCLUSIONS

Partial tendon lacerations involving 90 percent of the cross-sectional area can be safely treated without surgical repair and immediate protected active motion. Indications for exploration and treatment include concern for complete injury, triggering of the involved digit, or entrapment of the tendon. Surgical treatment for tendon triggering or entrapment with less than 75 percent cross-sectional injury is beveling of the tendon edges and injuries greater than 75 percent should be repaired with a noncircumferential, simple epitendinous suture. All patients should be allowed to perform early protected active motion after surgery.

Accuracy of Visual Estimates of Partial Flexor Tendon Lacerations

PURPOSE

To determine whether hand surgeons could accurately and consistently estimate the size of partial flexor tendon lacerations.

MATERIALS AND METHODS

Thirty-two partial flexor tendon lacerations were made in the flexor digitorum profundus tendons of a fresh-frozen cadaveric hand. Four hand surgeons and 5 residents estimated the size of the lacerations. Estimates were repeated 3 days later. Magnified images of the laceration cross-section were used to calculate the true size of each laceration. Inter- and intrarater reliability were calculated using the intraclass correlation coefficient. Accuracy was measured with the mean bias error and the mean absolute error.

RESULTS

Interrater and intrarater reliabilities were both high. There was a high level of consistency for both surgeons and residents. In terms of accuracy, there was a 3% bias toward underestimation. The mean absolute error was 11%. There was no statistically significant difference between the accuracy of attending hand surgeons and that of residents. Participants were less accurate when estimating lacerations close to a 60% laceration threshold for surgical repair (lacerations in the 50%-70% range). For lacerations within this range, an incorrect management decision would have been made 17% of the time, compared with 7% of the time for lacerations outside that range.

CONCLUSIONS

The accuracy and reliability of surgeon estimates of partial flexor tendon laceration size were high for surgeons and residents. Accuracy was lower for lacerations close to the threshold for repair.

CLINICAL RELEVANCE

Visual estimation is acceptable for evaluating partial flexor tendon lacerations, but it may be less reliable for lacerations near the threshold for repair. Therefore, surgeons should be cautious when deciding whether or not to repair partial lacerations in the borderline range.

Effect of triggering and entrapment on tendon gliding properties following digital flexor tendon laceration: in vitro study on turkey tendon

The optimal management of partial flexor tendon laceration is controversial and remains a clinical challenge. Abnormal tendon gliding (triggering and entrapment) was assessed at the A2 pulley in 40 turkey tendons in three groups: intact, partially divided (palmar or lateral), and trimmed. Testing was of gliding resistance and friction coefficient at 30° and 70° of flexion, loaded with 2 and 4 N. We observed for triggering and entrapment. The changes in gliding properties were compared and analysed using Wilcoxon matched pair testing. A significant difference was found in the change in gliding properties of intact to lacerated and lacerated to trimmed tendons and between tendons that glided normally compared with those exhibiting triggering or entrapment. This suggests that palmar and lateral lacerations which, through clinical examination and visualization, are found to glide normally should be treated with early mobilization. However, partial lacerations that exhibit triggering or entrapment should be trimmed.

Effect of core suture technique and type on the gliding resistance during cyclic motion following flexor tendon repair: a cadaveric study

We investigated the effects of two suture techniques using three suture types in a human model in vitro. We obtained 60 flexor digitorum profundus (FDP) tendons from cadavers and measured the gliding resistance during 1,000 cycles of simulated flexion-extension motion and load to failure of six groups: the modified Kessler (MK) repair using 3-0 coated, braided polyester (Ethibond, Ethicon, Somerville, NJ), 3-0 coated, braided polyester/monofilament polyethylene composite (FiberWire®; Arthrex, Naples, FL), or 4-0 FiberWire; and the Massachusetts General Hospital (MGH) repair using 3-0 Ethibond, 3-0 FiberWire, or 4-0 FiberWire. The 3-0 Ethibond MGH suture had significantly higher ultimate load to failure than the 3-0 or 4-0 FiberWire MK suture. The 3-0 and 4-0 FiberWire MGH sutures had significantly higher load to failure than the three MK groups. The gliding resistances of the three MGH groups were significantly higher than that of the three corresponding MK groups. The MGH repair had more gliding resistance than an MK repair, even when comparing large diameter suture in the MK repair with smaller diameter suture in the MGH repair. In this study, suture technique was more important in predicting repair load to failure and gliding resistance than the nature or caliber of the suture material that was used.

Effect of laceration and trimming of a tendon on the coefficient of friction along the A2 pulley

We carried out lacerations of 50%, followed by trimming, in ten turkey flexor tendons in vitro and measured the coefficient of friction at the tendon-pulley interface with loads of 200 g and 400 g and in 10°, 30°, 50° and 70° of flexion. Laceration increased the coefficient of friction from 0.12 for the intact tendon to 0.3 at both the test loads. Trimming the laceration reduced the coefficient of friction to 0.2. An exponential increase in the gliding resistance was found at 50° and 70° of flexion (p = 0.02 and p = 0.003, respectively) following trimming compared to that of the intact tendon.

We concluded that trimming partially lacerated flexor tendons will reduce the gliding resistance at the tendon-pulley interface, but will lead to fragmentation and triggering of the tendon at higher degrees of flexion and loading. We recommend that higher degrees of flexion be avoided during early post-operative rehabilitation following trimming of a flexor tendon.

Gliding resistance and strength of composite sutures in human flexor digitorum profundus tendon repair: an in vitro biomechanical study

PURPOSE

Although the strength of a tendon repair is clearly important, the friction of the repair is also a relevant consideration. The purpose of this study was to characterize the frictional coefficient, gliding resistance, and breaking strength of suture materials and a suture construct commonly used for flexor tendon repair.

METHODS

We measured the friction coefficients of 3-0 braided nylon enclosed in a smooth nylon outer shell (Supramid, S. Jackson, Alexandria, VA), 3-0 braided polyester coated with polybutilate (Ethibond, Ethicon, Somerville, NJ), and 3-0 braided polyester/monofilament polyethylene composite (FiberWire, Arthrex, Naples, FL) sutures. We also measured the gliding resistance, linear breaking strength, and resistance to gapping of zone 2 modified Pennington tendon repairs with the 2 lowest-friction sutures in 20 human cadaveric flexor digitorum profundus tendons.

RESULTS

The braided polyester/monofilament polyethylene composite had a significantly lower friction coefficient (0.054) than either the coated polyester (0.076) or nylon (0.130) sutures. The gliding resistances of the repaired tendons with braided/monofilament polyethylene composite suture and those of coated, braided polyester were similar. The strength of the 2 repairs (force to produce a 2 mm gap) and resistance to gap formation were also not significantly different.

CONCLUSIONS

Braided polyester composite is a low-friction suture material. However, when this suture was used for tendon repair with a locking suture technique, it did not show a significant effect on the gliding resistance and repair strength compared with the same repair using a coated polyester suture.

Evaluation of passive and active rehabilitation and of tendon repair for partial tendon lacerations after three weeks of healing in canines

BACKGROUND

Both passive and active rehabilitation have been shown to be superior to immobilization following partial tendon laceration, but few studies have directly compared these two rehabilitation protocols. In addition, controversy still remains over whether a partial tendon laceration should be repaired.

METHODS

We evaluated gap formation, adhesions, gliding function and structural properties of repaired and unrepaired tendons following 3 weeks of unrestricted active rehabilitation versus passive mobilization for partial laceration of canine flexor digitorum profundus tendons. An ex vivo radiographic method was used to measure tendon excursion and rotation at each finger joint. The tendon was examined for adhesions, and gapping was measured with calipers. The tendons were tensile tested to failure.

FINDINGS

We found no significant differences in tendon excursion, total joint rotation, or adhesions between any groups. Gap size was higher with active mobilization. We found no effect of rehabilitation protocol on the strength or stiffness of healing tendons at 3 weeks. Tendon repair did not affect tendon strength, but did produce higher stiffness in healing tendons at 3 weeks.

INTERPRETATION

The results indicate that active rehabilitation appears safe for partial lacerations less than 60 percent. Though repair appears to weaken the tendon in the early stages of healing, it may provide some biomechanical benefit by the middle stages of healing.

Treatment of partial lacerations in flexor tendons by trimming. A biomechanical in vitro study

BACKGROUND

Treatment of a partial laceration in zone 2 of a flexor tendon is controversial. The intact part of the tendon can usually sustain forces of normal unresisted motion, and repaired partially lacerated tendons can actually be weaker than unrepaired ones. However, complications such as triggering or entrapment have been reported in association with unrepaired tendons. The purpose of this study was to measure the biomechanical behavior following trimming of the tendon as an alternative to repair.

METHODS

Thirty-six flexor digitorum profundus tendons were harvested from sixteen unpaired fresh-frozen cadaveric human hands and were randomly assigned to be subjected to either 50% or 75% partial laceration, which was either lateral or volar, and were then assigned to no repair, repair with a running suture, or trimming. Mean and maximum gliding resistances were measured as the flexor digitorum profundus glided through the bone-A2 pulley complex and the flexor digitorum superficialis. Values were normalized to those measured in the intact tendon. The tendons were then distracted to failure, and maximum load and stiffness were recorded.

RESULTS

There was triggering or entrapment of eight unrepaired tendons; two cases were severe, and six were minor. When no severe trigger was obvious, the unrepaired tendons had the lowest tendency for gliding resistance, followed by the tendons treated with trimming and then by those treated with the running suture. Overall, the tendons with a volar laceration had higher mean and maximum gliding resistance than those with a lateral laceration (p < 0.05), those with a 75% partial laceration had higher mean gliding resistance than those with a 50% laceration (p < 0.05), and the tendons that were repaired with running suture had higher mean gliding resistance than those treated with trimming (p < 0.05). Tendon strength was not significantly different among the three types of treatment.

CONCLUSIONS

From the perspective of gliding resistance after partial tendon laceration, no repair appears necessary unless triggering is a problem. If triggering occurs, then trimming of a partially lacerated tendon may be a reliable alternative to repair, at least in terms of gliding resistance and strength.

Injury and repair of ligaments and tendons

In this chapter, biomechanical methods used to analyze healing and repair of ligaments and tendons are initially described such that the tensile properties of these soft tissues as well as their contribution to joint motion can be determined. The focus then turns to the important mechanical and biological factors that improve the healing process of ligaments. The biomechanics of surgical reconstruction of the anterior cruciate ligament and the key surgical parameters that affect the performance of the replacement grafts are subsequently reviewed. Finally, injury mechanisms and the biomechanical analysis of various treatment techniques for various types of tendon injuries are described.