Ligamentous healing potential of the acromioclavicular ligament following acute anatomical reconstruction.

BACKGROUND: Horizontal instability following acute acromioclavicular joint (ACJ) reconstruction still occurs with a high prevalence. Although the human acromioclavicular ligament complex (ACLC) represents the major horizontal ACJ stabilizer, experimental studies on healing characteristics are lacking. Therefore, the purpose of this histological study was to investigate the healing potential of the ACLC following acute anatomical reconstruction METHODS: In this prospective clinical-experimental study, 28 ACLC biopsies were performed in patients with complete ACJ dislocations (Rockwood type 4 or 5) during acute hook plate stabilization (IG: implantation group; n = 14) and hook plate removal (EG: explantation group; n = 14). Histological analyses included Giemsa staining, polarized light microscopy and immunostaining against CD68, αSMA and collagen type I and type III. Histomorphological evaluation entailed cell counts, collagen expression score, ligament tissue maturity index (LTMI) and descriptive analysis of specific ligamentous structures. Statistics consisted of nonparametric Mann-Whitney U tests and a level of significance of P < .05. RESULTS: Total cell counts (cells/mm2 1491 ± 296 vs. 635 ± 430; P < 0.001) and collagen III expression (3.22 ± 0.22 vs. 1.78 ± 0.41; P < 0.001) were higher in EG compared to IG. Inversely αSMA + (11 ± 9 vs. 179 ± 186; P < 0.001) and CD68 + cell counts (56 ± 20 vs. 100 ± 57; P 0.009) were significantly lower in the EG. The EG revealed a comparable reorientation of ligamentous structures. Consistently, ACLC samples of the EG (21.6 ± 2.4) displayed a high total but differently composed LTMI score (IG: 24.5 ± 1.2; P < 0.001). CONCLUSIONS: This experimental study proved the ligamentous healing potential of the human ACLC following acute anatomical reconstruction. Histomorphologically, the ACLC reliably showed a ligamentous state of healing at a mean of about 12 weeks after surgery. However, processes of ligamentous remodeling were still evident. These experimental findings support recent clinical data showing superior horizontal ACJ stability with additional AC stabilization in the context of acute ACJ reconstruction. Though, prospective clinical and biomechanical studies are warranted to evaluate influencing factors on ACLC healing and potential impacts of acute ACLC repair on clinical outcome. STUDY TYPE: Controlled Laboratory Study.

Current evidence base for kinematic alignment.

BACKGROUND: Kinematic alignment recently became an alternative alignment option for total knee arthroplasty (TKA). Beside previous studies assessing mechanical alignment in comparison to unintentional malalignment of TKA in terms of implant survival and clinical outcome, more and more studies have focused on the direct comparison of intentional kinematic alignment with mechanical alignment of the prosthesis. In the past 5 years the number of studies with respect to kinematic alignment has risen from 11 to 91 studies. AIM: The aim of this review article is to give a narrative overview of the current literature in the debate concerning kinematic and mechanical alignment in TKA.

[PSI-technique for kinematic alignment]. / PSI ­ Technik des kinematischen Alignments.

BACKGROUND: Compared with the current gold standard of knee endoprosthetics, the concept of kinematic alignment is more responsive to the individual anatomy of the patient as it enables the three-dimensional restoration of individual axes, joint lines and capsule tension. One point of criticism is the lack of intraoperative control over individual bone resections with conventional instrumentation. However, with the help of CT-based individual 3D-printed cutting blocks, a precise preoperative plan can be transferred to the operating room. The aim of this article is to explain the operative technique of patient-specific instrumentation (PSI)-protected kinematic alignment. METHODS: The procedure is based on a preoperative 3D model of the bony anatomy of the patient, with the aid of which the planning of the operation, with the positioning and size of the implant, as well as the necessary bone resections, are carried out. With this information about anatomy and resection levels the individual cutting blocks are produced, aided by a 3D printer. Intraoperative control is achieved by measuring the resection by means of a gage and comparison with the digital 3D design. DISCUSSION: With the aid of the 3D-printed PSI cutting blocks the preoperative plan of kinematic alignment can be implemented in a precise manner. It is a simple tool and does not require any great expense. Compared with the conventional instrumentation, the operating time is shortened. However, because of the purely CT-based design, no information about the state of the soft tissue is obtained.