The effect of the orientation of the radial head on the kinematics of the ulnohumeral joint and force transmission through the radiocapitellar joint

doi:10.1016/j.clinbiomech.2006.01.006

Clinical Biomechanics

Volume 21, Issue 6, July 2006, Pages 554-559

https://doi.org/10.1016/j.clinbiomech.2006.01.006 Get rights and content

Abstract

Background. The treatment of radial head fractures that are not amenable to an open reduction and internal fixation, remains to be a difficult issue. A potential problem with prosthetic replacement of the radial head is the shape of current radial head prostheses. The purpose of this study was to determine the effect of the shape of the radial head on kinematics and load transfer of the elbow.

Methods. Kinematics of the elbow and radiocapitellar force transmission were measured in 6 fresh frozen upper extremities. The effect of radial head shape was tested by rotating the head 90°, with a custom-made ‘native’ radial head prosthesis. 3-D spatial orientation of the ulna showed an average difference in ulnohumeral laxity, between the nominal and 90° conditions, of 0.1° throughout the arc of motion with neutral forearm rotation (maximum: 2°).

Findings. We found an average difference in ulnar axial rotation, of 0.1° (maximum: 1.9°). No differences showed statistical significance. Radiohumeral joint force was measured and maximally showed a 32 times increase of force in the altered shape conditions.

Interpretation. Our results show that the kinematics of the elbow was not affected by altering the shape of the radial head, but it did adversely affect the forces in the radiohumeral joint. This could possibly generate degenerative changes in the elbow.

Introduction

The treatment of radial head fractures that are not amenable to an open reduction and internal fixation remains a difficult issue. Resection of the radial head has been the gold standard in the past. Long-term studies show acceptable improvement in mobility and pain relief (Broberg and Morrey, 1986). Problems like proximal translation of the radius, often with accompanying wrist pain reduced forearm strength and ulnohumeral arthritis (Morrey et al., 1979), have led to the development of several types of radial head prostheses.

Currently, the main indication for implanting a radial head prosthesis is possible ulnohumeral instability, especially in the medial collateral ligament (MCL) deficient elbow (Van Glabbeek et al., 2001). However, no radial head prosthesis design has been shown to reproduce the stability, which the native radial head provides. Ulnohumeral arthritis, which is commonly found in long term follow-up studies after resection of the radial head, is so far not seen in patients with prosthetic replacement of the radial head. However, clinical reports on current radial head prosthesis have only been short-term and it is too early to predict if no arthritic changes will be found in the elbow at long term follow-up.

A potential problem with prosthetic replacement of the radial head is the shape of current radial head prostheses. All have a round radial head component, although the native radial head has an elliptic shape (van Riet et al., 2003). The purpose of this study was to determine the effect of the shape of the radial head on kinematics and load transfer of the elbow. This was achieved by altering the orientation of the radial head in the elbow and therefore essentially changing the shape.

Section snippets

Methods

Six fresh frozen upper extremities from cadavers with no macroscopic evidence of pathology were used. Range of motion and stability of the cadaver elbows were tested clinically and were considered to be within normal range. The specimens were thawed overnight at room temperature. The humerus was transected in its mid-portion and the wrist was disarticulated, preserving ligaments of the distal radio-ulnar joint. The shaft of the humerus was cemented into an acrylic tube. Heavy nylon sutures were

Results

Analysis of total varus–valgus laxity and total axial rotation, showed no significant differences, between the intact condition and the native condition with an intact MCL, throughout the flexion arc, in any flexion angle and in all three forearm rotations (P > 0.05), showing the validity of the procedure.

In the medial collateral deficient elbow, the total varus–valgus laxity measured in the nominal condition showed marked similarities to that in the 90° rotated position, for all three forearm

Discussion

A recent anatomic study showed significant differences between orthogonal diameters of the radial head (P < 0.01), indicating that the radial head is not round (van Riet et al., 2003). The kinematic effects of the shape, and therefore orientation, of the radial head has never before been studied in the MCL deficient elbow.

We found no significant differences in any of the kinematic parameters measured between the intact and nominal radial head conditions in any flexion angle in all three rotations

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Cited by (43)

Ulnohumeral joint static cartilage compression is affected by radial head implant size
2023, Clinical Biomechanics
Citation Excerpt :
Notably, little data exists in the literature to validate the use of interposed sensors in measuring the static unloaded forces in a joint or CRCF. Few studies have evaluated effect of forearm position on the elbow joint, and most focus on RCJ mechanics (Ahmad et al., 2004; Pomianowski et al., 2001; Seiber et al., 2009; Van Glabbeek et al., 2004; Van Riet et al., 2006). To our knowledge no work looks at the effect on the UHJ noninvasively after RHA.
Radiocapitellar joint arthroplasty is a commonly performed procedure, which often leads to early failure or instability. Few studies assess the effect of radiocapitellar joint arthroplasty on the ulnohumeral joint. We hypothesized that static forces of contact (compressing cartilage, or cartilage relaxation contact force) would reveal the effect of varying radial head implant size and elbow position on the ulnohumeral joint.
A minimally–invasive method of measuring cartilage relaxation contact force was utilized in 10 fresh-frozen human cadaveric specimens that did not require significant dissection or intraarticular sensor placement. Specimens were rigidly fixed in various positions of elbow flexion and forearm pronosupination with increasing radial head implant lengths. Uniaxial distracting forces were applied and displacement was repeatedly measured with resultant best-fit polynomial curves to determine inflections corresponding to the force required to overcome static cartilage relaxation as in previous work.
Baseline mean (intra-cadaver) cartilage relaxation contact force was 11.8 N (standard error of the mean = 0.3) at 90° of elbow flexion and neutral rotation. There was little variation within specimens (Intraclass correlation coefficient > 0.94). Cartilage relaxation contact force increased at the ulnohumeral joint with radial head implant overstuffing (> 4 mm, P < 0.05) and elbow flexion (120°, P < 0.001). Pronosupination altered cartilage relaxation contact force in an implant-length independent manner (P < 0.05).
Radiocapitellar joint arthroplasty implant length and elbow joint position independently contribute to increased cartilage relaxation contact force at the ulnohumeral joint. This further supports attempts at anatomic reconstruction of the radiocapitellar joint to prevent pathologic ulnohumeral joint loading.
A radial head prosthesis that aligns with the forearm axis of rotation: a retrospective multicenter study
2022, Seminars in Arthroplasty JSES
Advancements in technique and devices and a better understanding of forearm kinematics have contributed to the improvement in outcomes following radial head arthroplasty. The results of radial head arthroplasty depend on the inherent variability of the proximal radial anatomy and on the subsequent difficulties in attaining anatomic positioning of the prosthesis. A monobloc prosthesis with an anatomical head that is aligned with the patient’s axis of forearm rotation has been recently introduced. We report the clinical and radiographic outcomes for patients across multiple centers who received this radial head implant with a minimum of 2-year follow-up.
This was a multi-institution retrospective follow-up including 6 centers and multiple surgeons. A total of 114 cases were performed prior to July 20, 2019, of which 52 (46%) responded to request for follow-up. Data collected included Mayo Elbow Performance Score, Disabilities of the Arm, Shoulder and Hand scores, visual analog scale (VAS) for pain, major complications, and reoperations. Major complications were defined as any prosthesis-related event which may or may not have required reoperation.
The mean Mayo Elbow Performance Score was 87.0 (range, 55-100), with 46% (24/52) scoring a 100. The mean VAS for pain at rest was 0.9 (range, 0-10), and the mean VAS for pain while unscrewing a bottle cap was 1.9 (range, 0-10). The mean Disabilities of the Arm, Shoulder and Hand score was 19.6 (range, 0-88.6). We recorded a total of 4 major complications, 3 of which required reoperations, for a rate of 7.6% and 5.7%, respectively.
The current results, collected from 6 institutions and multiple surgeons, are comparable to those of other similar series for radial head prostheses. Our series had lower rates of complications and reoperations. There were no cases of stem loosening. The alignment of the radial head to the forearm axis of rotation may restore forearm kinematics. This design may lead to radiocapitellar contact pressures that are more physiologic in load transmission.
Design of Anatomical Population-Based and Patient-Specific Radial Head Implants
2017, Journal of Hand Surgery
The objective of this study was to characterize the morphology of the radial head and design population-based anatomical and patient-specific radial head implants.
Computed tomography (CT) images of 50 normal cadaveric upper extremities (34 male, 16 female) were obtained using a 64-slice CT scanner. Surface models were ellipse-fitted and characterized. Using an intersurface distance mapping approach, the surface geometry of the population-based anatomical design (PB-An), 3 distinct patient-specific designs, and an existing axisymmetrical implant (Com-Axi) were compared with the native radial head and the overall surface mismatch was measured.
Morphological analysis indicated that the diameters of the outer and rim ellipses were correlated. The mean mismatch for the existing commercially available axisymmetrical implants was 0.5 ± 0.1 mm.The PB-An implants showed significantly reduced surface mismatch (0.4 ± 0.2 mm). The PS-An implant using 82 parameters in its design (0.1 ± 0.0 mm), had the lowest mean surface mismatch of any of the implants investigated.
The mean surface mismatch of radial head implants may be reduced using reverse engineering techniques to determine the required parameters for both population-based and patient-specific implant designs. Whether there is a significant clinical advantage of a more anatomically shaped radial head implant requires additional study. More anatomical implant shapes rely on a surgical technique to accurately position these implants during surgery. It is unclear if this can be achieved clinically using conventional techniques or whether computer-assisted surgery will be required to realize the potential advantages of a more anatomical implant.
This study characterized the morphology of the radial head with implications for population-based anatomical implants and patient-specific implants. The overall design of each implant was quantitatively compared with the native radial head. This study has implications for the design of patient-specific/anatomical implants and compares their use with commercially available generic implants.
The Effect of Elbow Extension on the Biomechanics of the Osseoligamentous Structures of the Forearm
2015, Journal of Hand Surgery
To investigate the hypothesis that elbow extension alters the biomechanics of forearm rotation including force transmission in the distal and proximal radioulnar joints (DRUJ and PRUJ) and the interosseous ligament (IOL).
A cadaver model with a custom-designed jig was used to measure forearm pronosupination ranges, transmitted forces and contact areas across the PRUJ and DRUJ, and tension in the 3 main components of the IOL's central band. Testing with applied loads was undertaken throughout pronosupination with the elbow fully flexed (n = 15) and fully extended (n = 11).
Elbow extension-flexion affected the range of forearm pronosupination, shifting the arc of rotation such that the forearm supinated maximally with the elbow flexed and pronated maximally with the elbow extended. Elbow extension also increased transmitted forces across the DRUJ and PRUJ while also increasing contact areas within the DRUJ and PRUJ. Elbow extension significantly increased tension in the central band of the IOL when the forearm was maximally pronated.
Maximum supination occurred with the elbow flexed. Maximum pronation occurred with it extended. Elbow position altered forearm biomechanics, including force transmission across the PRUJ and DRUJ and transmitted tension in the IOL.
The interplay of osseoligamentous forearm structures is such that we would anticipate surgical alteration of any one of them to have effects upon function of the others.
Effect of radial head implant shape on joint contact area and location during static loading
2015, Journal of Hand Surgery
Citation Excerpt :
Bipolar radial heads contain a joint between the head and stem of the implant, allowing some tilting of the dish.9 Some axisymmetric implants employ a smooth stem that is purposely placed loose so that the head can move small amounts and essentially self-align with the capitellum.7 Anatomic implants are equipped with markings to try to aid in the best possible alignment.10
To examine the effect of implant shape on radiocapitellar joint contact area and location in vitro.
We used 8 fresh-frozen cadaveric upper extremities. An elbow loading simulator examined joint contact in pronation, neutral rotation, and supination with the elbow at 90° flexion. Muscle tendons were attached to pneumatic actuators to allow for computer-controlled loading to achieve the desired forearm rotation. We performed testing with the native radial head, an axisymmetric implant, a reverse-engineered patient-specific implant, and a population-based quasi-anatomic implant. Implants were inserted using computer navigation. Contact area and location were quantified using a casting technique.
We found no significant difference between contact locations for the native radial head and the 3 implants. All of the implants had a contact area lower than the native radial head; however, only the axisymmetric implant was significantly different. There was no significant difference in contact area between implant shapes.
The similar contact areas and locations of the 3 implant designs suggest that the shape of the implant may not be important with respect to radiocapitellar joint contact mechanics when placed optimally using computer navigation. Further work is needed to explore the sensitivity of radial head implant malpositioning on articular contact. The lower contact area of the radial head implants relative to the native radial head is similar to previous benchtop studies and is likely the result of the greater stiffness of the implant.
Radial head implant shape does not appear to have a pronounced influence on articular contact, and both axisymmetric and anatomic metal designs result in elevated cartilage stress relative to the intact state.
The effect of prosthetic radial head geometry on the distribution and magnitude of radiocapitellar joint contact pressures
2015, Journal of Hand Surgery
To determine if radiocapitellar contact pressures would be elevated with nonanatomical (circular) prostheses over those mimicking native anatomy and if such pressures would be related to the depth and contour of the articular dish and to the pattern of prosthetic articulation against the lateral trochlear ridge.
Three commercially available circular radial head designs were compared with an anatomical radial head and 2 modified anatomical prototype radial head designs in 10 cadaveric specimens. Each prosthesis and specimen combination was loaded in neutral rotation and maximal extension with a custom testing apparatus while measuring contact areas and pressures using thin-film pressure sensors.
Anatomical radial head prototype 2 had similar radiocapitellar contact areas and mean pressures as the native radial head; all other designs showed significant decreases in contact area and increased mean pressures. Peak contact pressures were also measured and were significantly elevated with all prostheses tested. Anatomical designs are statistically more likely to mimic normal contact with the lateral trochlear ridge and its adjacent sulcus than circular prostheses. They are also significantly less likely to have contact pressures above the 5 MPa threshold that is thought to be harmful to cartilage. The depth of the articular dish had a significant effect on contact area and pressure.
Commercially available radial head prostheses demonstrated reduced radiocapitellar contact areas and elevated contact pressures during compressive loading. These were significantly greater with symmetrical circular prostheses than with asymmetrical elliptical designs. The prosthesis that best mimicked native contact behavior was the anatomical radial head prototype 2 owing to its design for articulating with the capitellum, the lateral trochlear ridge, and the sulcus between.
Because radial head prostheses have the potential to cause capitellar erosion or arthritic change, those with lower contact pressures may lead to fewer such complications.

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The effect of the orientation of the radial head on the kinematics of the ulnohumeral joint and force transmission through the radiocapitellar joint

Abstract

Introduction

Section snippets

Methods

Results

Discussion

J. Biomech.

Clin. Biomech.

Clin. Biomech.

J. Hand Surg. Am. A

Clin. Biomech.

Results of delayed excision of the radial head after fracture

J. Bone Joint Surg. Am.