Post-traumatic elbow rotational stiffness

Muscle does not drive persistent posttraumatic elbow contracture in a rat model

INTRODUCTION

Posttraumatic elbow contracture is clinically challenging because injury often disrupts multiple periarticular soft tissues. Tissue specific contribution to contracture, particularly muscle, remains poorly understood.

METHODS

In this study we used a previously developed animal model of elbow contracture. After surgically inducing a unilateral soft tissue injury, injured limbs were immobilized for 3, 7, 21, and 42 days (IM) or for 42 IM with 42 days of free mobilization (42/42 IM-FM). Biceps brachii active/passive mechanics and morphology were evaluated at 42 IM and 42/42 IM-FM, whereas biceps brachii and brachialis gene expression was evaluated at all time points.

RESULTS

Injured limb muscle exhibited significantly altered active/passive mechanics and decreased fiber area at 42 IM but returned to control levels by 42/42 IM-FM. Gene expression suggested muscle growth rather than a fibrotic response at 42/42 IM-FM.

DISCUSSION

Muscle is a transient contributor to motion loss in our rat model of posttraumatic elbow contracture. Muscle Nerve 58:843-851, 2018.

Posttraumatic Elbow Stiffness: A Critical Analysis Review

Open and arthroscopic release are both effective surgical treatments for posttraumatic elbow stiffness. Both static and dynamic bracing are effective for increasing elbow range of motion when heterotopic ossification is not present. Some loss of immediate postoperative range of motion is expected. Recurrence of heterotopic ossification around the elbow is rare. The occurrence of ulnar nerve palsy is rare and often requires transposition.

Temporal Patterns of Motion in Flexion-extension and Pronation-supination in a Rat Model of Posttraumatic Elbow Contracture

BACKGROUND

The elbow is highly susceptible to contracture, which affects up to 50% of patients who experience elbow trauma. Previously, we developed a rat model to study elbow contracture that exhibited features similar to the human condition, including persistently decreased ROM and increased capsule thickness/adhesions. However, elbow ROM was not quantitatively evaluated over time throughout contracture development and subsequent mobilization of the joint.

QUESTIONS/PURPOSES

The purposes of this study were (1) to quantify the time-dependent mechanics of contracture, including comparison of contracture after immobilization and free mobilization; and (2) to determine what changes occur in capsule and joint surface morphology that may support the altered joint mechanics.

METHODS

A total of 96 male Long-Evans rats were randomized into control and injury (unilateral soft tissue injury/immobilization) groups. Flexion-extension and pronation-supination joint mechanics (n = 8/group) were evaluated after 3, 7, 21, or 42 days of immobilization (IM) or after 42 days of IM with either 21 or 42 days of free mobilization (63 or 84 FM, respectively). After measuring joint mechanics, a subset of these limbs (n = 3/group) was prepared for histologic analysis and blinded sections were scored to evaluate capsule and joint surface morphology. Joint mechanics and capsule histology at 42 IM and 84 FM were reported previously but are included to demonstrate the full timeline of elbow contracture.

RESULTS

In flexion-extension, injured limb ROM was decreased compared with control (103° ± 11°) by 21 IM (70° ± 13°) (p = 0.001). Despite an increase in injured limb ROM from 42 IM (55° ± 14°) to 63 FM (83° ± 10°) (p < 0.001), injured limb ROM was still decreased compared with control (103° ± 11°) (p = 0.002). Interestingly, ROM recovery plateaued because there was no difference between injured limbs at 63 (83° ± 10°) and 84 FM (73° ± 19°) (p > 0.999). In pronation-supination, increased injured limb ROM occurred until 7 IM (202° ± 32°) compared with control (155° ± 22°) (p = 0.001), representative of joint instability. However, injured limb ROM decreased from 21 (182° ± 25°) to 42 IM (123° ± 47°) (p = 0.001), but was not different compared with control (155° ± 22°) (p = 0.108). Histologic evaluation showed morphologic changes in the anterior capsule (increased adhesions, myofibroblasts, thickness) and nonopposing joint surfaces (surface irregularities with tissue overgrowth, reduced matrix), but these changes did not increase with time.

CONCLUSIONS

Overall, flexion-extension and pronation-supination exhibited distinct time-dependent patterns during contracture development and joint mobilization. Histologic evaluation showed tissue changes, but did not fully explain the patterns in contracture mechanics. Future work will use this rat model to evaluate the periarticular soft tissues of the elbow to isolate tissue-specific contributions to contracture to ultimately develop strategies for tissue-targeted treatments.

CLINICAL RELEVANCE

A rat model of posttraumatic elbow contracture quantitatively described contracture development/progression and reiterates the need for rehabilitation strategies that consider both flexion-extension and pronation-supination elbow motion.

Pronation-Supination Motion Is Altered in a Rat Model of Post-Traumatic Elbow Contracture

The elbow joint is highly susceptible to joint contracture, and treating elbow contracture is a challenging clinical problem. Previously, we established an animal model to study elbow contracture that exhibited features similar to the human condition including persistent decreased range of motion (ROM) in flexion-extension and increased capsule thickness/adhesions. The objective of this study was to mechanically quantify pronation-supination in different injury models to determine if significant differences compared to control or contralateral persist long-term in our animal elbow contracture model. After surgically inducing soft tissue damage in the elbow, Injury I (anterior capsulotomy) and Injury II (anterior capsulotomy with lateral collateral ligament transection), limbs were immobilized for 6 weeks (immobilization (IM)). Animals were evaluated after the IM period or following an additional 6 weeks of free mobilization (FM). Total ROM for pronation-supination was significantly decreased compared to the uninjured contralateral limb for both IM and FM, although not different from control limbs. Specifically, for both IM and FM, total ROM for Injury I and Injury II was significantly decreased by ∼20% compared to contralateral. Correlations of measurements from flexion-extension and pronation-supination divulged that FM did not affect these motions in the same way, demonstrating that joint motions need to be studied/treated separately. Overall, injured limbs exhibited persistent motion loss in pronation-supination when comparing side-to-side differences, similar to human post-traumatic joint contracture. Future work will use this animal model to study how elbow periarticular soft tissues contribute to contracture.

Persistent motion loss after free joint mobilization in a rat model of post-traumatic elbow contracture

BACKGROUND

Post-traumatic joint contracture (PTJC) in the elbow is a challenging clinical problem due to the anatomical and biomechanical complexity of the elbow joint.

METHODS

We previously established an animal model to study elbow PTJC, wherein surgically induced soft tissue damage, followed by 6 weeks of unilateral immobilization in Long-Evans rats, led to stiffened and contracted joints that exhibited features similar to the human condition. In this study, after 6 weeks of immobilization, we remobilized the animal (ie, external bandage removed and free cage activity) for an additional 6 weeks, after which the limbs were evaluated mechanically and histologically. The objective of this study was to evaluate whether this decreased joint motion would persist after 6 weeks of free mobilization (FM).

RESULTS

After FM, flexion-extension demonstrated decreased total range of motion (ROM) and neutral zone length, and increased ROM midpoint for injured limbs compared with control and contralateral limbs. Specifically, after FM total ROM demonstrated a significant decrease of approximately 22% and 26% compared with control and contralateral limbs for injury I (anterior capsulotomy) and injury II (anterior capsulotomy with lateral collateral ligament transection), respectively. Histologic evaluation showed increased adhesion, fibrosis, and thickness of the capsule tissue in the injured limbs after FM compared with control and contralateral limbs, which is consistent with patterns previously reported in human tissue.

CONCLUSION

Even with FM, injured limbs in this model demonstrate persistent joint motion loss and histologic results similar to the human condition. Future work will use this animal model to investigate the mechanisms responsible for PTJC and responses to therapeutic intervention.