Postoperative malrotation of humerus shaft fracture causes degeneration of rotator cuff and cartilage

Abstract

We hypothesized that postoperative malrotation of humeral shaft fractures can alter the bio-mechanical environment of the shoulder; thus, rotator cuff and cartilage degeneration could be induced. Therefore, we designed an animal experiment to evaluate the impact of malrotation deformities after minimally invasive surgery for humeral fractures on the rotator cuff and cartilage, which has rarely been described in previous studies. Twenty-four New Zealand white rabbits were randomly divided into the sham control group (A), negative control group (B) and malrotated group (C). A sham operation with surgical exposure alone was performed in group A. Humeral shaft osteotomy was performed in Group B and C. In Group B, the fractures were fixed in situ with plate -screw system. While in Group C, iatrogenic rotational deformity was created after the proximal end of the fracture being internally rotated by 20 degrees and then subsequently fixed. The animals with bone healing were sacrificed for pathological and biochemical examination. In group C, the modified Mankin scale for cartilage pathology evaluation and the modified Movin scale for tendon both showed highest score among groups with statistical significance (P < 0.05); Disordered alignment and proportion of collagen I/III of rotator cuff were confirmed with picrosirius red staining; Transmission electron microscopy also showed ultrastructural tendon damage. Immunohistochemistry showed that both MMP-1 and MMP-13 expression were significantly higher in group C than groups A and B(P < 0.05). Minimally invasive techniques for humerus shaft fracture might be cosmetically advantageous, but the consequent postoperative malrotation could increase the risk of rotator cuff and cartilage degeneration. This conclusion is supported here by primary evidence from animal experiments.

A finite element model of the shoulder: application to the changes of biomechanical environment induced by postoperative malrotation of humeral shaft fracture

“…The results of our model analysis are consistent with the above research results, and the peak stress of the scapular glenoid during external rotation in the state of rotational deformity appears in the posterior and inferior part, which is consistent with the epidemiological characteristics that the main wear of shoulder arthritis occurs in the posterior and inferior part of the scapular glenoid and two-thirds of the upper humeral head [ 7 ]. And we also had confirmed through animal experiments that rotational deformity of humeral fracture can lead to degeneration of articular cartilage and rotator cuff, which is consistent with the results of this study [ 6 ].…”

“…[ 5 ] prospectively analyzed 45 cases with humeral shaft fracture and found that 27.2% of patients who underwent IMN were present with 20° or more internal malrotation of the humeral head. And We also reported even a much higher incidence of 40.9% in the MIPO group [ 6 ]. Defects in muscle strength, changes in range of motion (ROM) and degenerative arthritis of the shoulder have been reported as consequences of postoperative malrotation of humeral shaft fractures.…”

Assessment of Intraoperative Rotational Alignment of Closed Locked Intramedullary Nailing for Humerus Fractures

“…17 Although beneficial in these circumstances, the increased rates of malrotation present from IMN remain an area of concern for this procedure because of the long-term effects of malrotation on the glenohumeral joint. 8 In fact, Wang et al 18 used an animal model to study the effects of malrotation on the shoulder and demonstrated that malrotating the humerus by 20 degrees led to early degenerative effects of both the cartilage along with the rotator cuff. In a similar way, Flury and colleagues retrospectively reviewed 34 patients undergoing weber's osteotomy for anteroinferior shoulder instability and found a significant relationship between degree of internal rotation and osteoarthritis disease severity.…”

Therapie von Humerusschaftfrakturen

“…Zwar sind die Auswirkungen entsprechender Rotationsfehler nicht hinreichend untersucht, dennoch weisen einzelne Studien auf schlechtere funktionelle Ergebnisse und einen eingeschränkten Bewegungsradius hin [61,62,63]. Darüber hinaus können Rotationsfehler zur Degeneration der Rotatorenmanschette und des artikulären Knorpels beitragen [72].…”